Technical Field
The present invention relates to a damper disc assembly, particularly to a damper disc assembly configured to transmit a torque inputted thereto from an engine toward a transmission.
Background Art
In general, noises and vibrations of vehicles include noises in idling, noises in traveling and tip-in/tip-out (low frequency vibrations). Damper disc assemblies are provided for inhibiting the aforementioned noises and vibrations.
In torsional characteristics of a damper disc assembly, a low torsion angular range relates to noises in idling, and a low torsional stiffness is preferable in the low torsion angular range. On the other hand, to countermeasure tip-in/tip-out, the torsional characteristics are required to have a highest possible stiffness.
To solve the aforementioned problems, there has been produced a type of damper disc assembly using two kinds of springs so as to implement two-stage torsional characteristics. This device is configured to suppress low both torsional stiffness and hysteresis torque in the first stage (low torsion angular range) of the torsional characteristics so as to inhibit noises in idling. Additionally, this device is configured to set both torsional stiffness and hysteresis torque to be high in the second stage (high torsion angular range) of the torsional characteristics so as to attenuate vibrations of tip-in/tip-out.
Moreover, there has been also produced a type of device in which a sub-damper unit is mounted laterally on the inner peripheral side of a main damper unit so as to particularly widen the first stage low torsion angular range as much as possible (see e.g., Japan Laid-open Patent Application Publication No. 2000-179574). Here in the well-known damper disc assembly, a spline hub is divided into a hub and a flange, and the divided hub and flange are coupled by the sub-damper unit in a rotational direction.